Radio direction finding



JunelG, 1947. D. G. c. LUCK v 2,422,109,

RADIO DIRECTION FINDING /HICK Gtforne'g June 10, 1947. D. G. c. LUCK V lRADIO DIRECTION FINDING Filed sept. 11, 1942 s sheets-sheet 2 0 Ohw .Qmsiirii ,SNF f 9 H .x u BEHH n ,.uue ir:. f|| w11# 1| f 0 1 A 1I }I| }1 IA- e rhwllullv IIIV I l k i|l a -T II ,|II| ||II llllll Il @gwwillllllmlllrfi: f lrlLr n wwwa @n Q @MMMQ Smm nvgntor UAE/1n Elfi/UDA;

(Ittorneg 3 Sheets-Sheet 3 t RMN June 10, 1947. D. G.`C. LUCK 'RADIODIRECITION FINDING Filed sept. 11, 1942 Patented June 10, 1947 UNITEDSL'ETES RADIO'DIRECTION FINDING paviaV o. o. Luck, MerchantviuafN. J.,assigner of America,.a corporation to Radio Corporation of DelawareThis` invention. relates to radio direction finding, and moreAparticularly to a system for recording. automatically the time andorigin of radio.. transmissions. at a` selected frequency. A system. ofthis type is..applicable, for example, in the operation of aircraft,vwhen ground personnel are to. he keptiinormed of the positionsV ofaircraft in iiightwithout special efiorton the part of thepilots.Generally a common frequency will be used for transmissions madeby anyof a group of aircraft, so, thatbearingsfor each member of the grouplmay be taken. Without retuning. 1\.Ievertl'1eless,.whenbearingsv arevtaken or recorded manually, some may be missed by the ground operator,due to. the fact that he is occupied with other duties, and.transmissions from aircraft in iiight. are customwily very brief.

Amechanically spinning antennaY type of direction finder-may beadaptedto record the bearings of received sign-als. The scanning drum oil i Fig. l is a. schematic diagram of a systemema-facsimilerecorder ismounted on an` extension of the antenna shaft. The received signals aremodulated by the rotation of the. directive antenna. A series of currentimpulses having, for example, the phase oi the modulation maxima may bederived by applying the modulated signal to a peak amplifier orequivalent device. The impulses are applied to the `printer circuitofthe facsimile recorder, producing a series of.-dots wheneverasignalisreceived. The positionof. the dots along thescanning line ofthe recorder will indicate theA azimuth of arrival of the signal.

For position. finding,y two intersecting, bearings, from differentlylocated receivers, are required.

and three are desirable to provide a check. All

three receivers shouldibe controlled from a central point, and presenttheir indications at that point.

Accordingly,y it isan object of this. invention to provide an improvedmethod of and means for recording bearings.

Another object is to provide asystem for recording automatically thebearings of a transmitter -withrespect toa plurality ofdifferentlylocatedreceivers.

A further object is: to provide an improved method of and means foractuating a facsimile recorder` in. response tothe outputs of aplurality of remote automatic direction iinders, producing simultaneous.but readily distinguishable records upon a common medium.

These and other and incidental objects will become apparaenttothoseskilled in the art upon considerationof the. following description, withreference to the accompanying. drawings, of which.

bodying the. invention; Fig.. 2 is a representation of a portion of a.typicalrecord producedbyl the system of' Fig. 11; and: Fig. 3.1is ablock diagram ofV a modification of theinvention.

Referring to F-ig, 1, .a remotev directionfinder station I. is shown,separated from theremainder of the drawing by a dashedline 2. Two otheridentical stations, not` shown, aire placed. at other locations andconnected to a. controlstation through. telephone or similar lines inthe same manner as the station I. Each directionA iinder comprises. Vaplurality .of stationary antennas N, E, S, and W,.co-nnected throughbalanced-modulators 3 and. 5to. a.. radioV receiver 1.Thigarran-gement.isdescribedlin detail. in U. S.1Pat`ent. 2,208,378.which issued to D.. G. C. Luck. and is assignedto. the same, assignee.as the instant ap.- plication. A centrally located antenna. Cfisprovided` for sense; determination and is connected tothe. receiver'lY through a modulating amplier 9.

Thecontrol station equipment includes. a. facsimile recorder II, whichmay be of the type described in. U; S... application Ser, No..42059.17,` iiled November 29, 1941i, by C.V J. Young., A motor I3 is.arranged todriyethe recorder I-'I, and alsofapair. of .commutatordevicesA |5'and Il.. The con'irnutator I5- may be driven directly fromthe motor |13. at 'a relatively high speed, and theV commutator. Ilisfdriven througha. gear reduction Il!! atv aA relatively low speed.A Adirect currentsourceY 23 is connected to the commutators. l5 and. I1,which are provided with. a plurality o separate circuit. making .andbreaking devices, Vconnected between the. direct current source 23 andmixer 61?',` through. wires Z5 and 3U; The commutators I5and.I II'may bephotoelectric to avoid.l contact troubles. Y Asecond directcurrentsource ZI isconnected' through separate circuit making andbreaking. means on the commutatordevice ltdiilters 69. and 1I.. The.output of the iilter 69 is suppliedv through a phase adjuster 'I3 and.ant amplitude adjuster 15'to a li'ne 'I'I'leading to the'modulation`input circuit of the balanced modulator 5 at thev remotgdirectioniinderstation I'. The output. of the iilter .'I-I. is similarly appliedthrough aphase adjuster 19, anamplitudev adjuster 8l, and line 83;]tothe, modulation input circuit of the balanced modulator 3'.

TheY two circuits from the filters 69 and' I'I are also ccnnectedthroughamplitude adjusters 85 y and 8T' to a mixer 89. The. devices 85 andi8'lare nder I is conducted over a line 33 to the control station. The otherremote stations' are similarly connected to lines 35 and 31. f The`line..

tern rotation component. The impulse generator 4I is controlled by the20 cycle wave to provide an impulse train in phase with, for example,the peaks of the 20 cycle wave. This impulse train passes through themixer 65 and actuates the facsimile recorder II to produce a dot on therecord each time the direction finder I scans past the line of signalarrival. The scanning drum of the recorder is operating at 1200 R. P. M.or 20 times per second; hence one dot is recorded during each scanningcycle. Successive dots will dene a line on the record, in a positioncor- 33 is connected through a filter 39 to an impulse generator 4I,which may be of the type described in U. S. Patent No. 2,188,611 whichissued to L. E. Norton and is assigned to the same *as-V signee as theinstant application. The line 35 is connected through a lter A43 andphase Shifters 45 and 41 to impulse generators 49 and 5I, as shown. Theline 31 is connected through a lter 53 to an impulse generator 55, andthrough phase Shifters 51 and 59 to impulse generators 6I and'63,respectively. The outputs of all of the impulse generators are appliedto a mixer 65. The output of the mixer B5 is connected,fto gether withthat of the mixer 61, to the printer circuit of the recorder I I.

The'adjustment and operation of the system is as follows: By way ofexample, the motor I3 'l is run at .1200 R. P. M., driving Vthe recorderII to provide one scanning stroke Aper revolution (i. e., 20 strokes persecond) and a paper feed rate of 36 centimeters per hour. The commutatorI5 is driven directly by the motor I3 and, in addition to otherfunctions described below, breaks up the voltage from the source 2l intotwo 20 cycle per second square wave trains which are delivered on theleads 3l and 432 inquadrature phase. The filters 69 andwl'l remove theharmonic components of the square waves providing substantiallysinusoidal waves to the phase adjusters 13" and 19, respectively. Thedevices 13 and 19 are manually adjusted to provide .exact quadraturerelationship between the two, wave trains, and the amplitude controlsand 8l are adjusted to makethe two Wavesequal in amplitude. The balanced.modulators 3 and 5 arecontrolled by the respective cycle per secondwaves to provide the eectof a single unidirectional Vantenna rotating at20 revolutions per second, as described in the aforementioned LuckPatent 2,208,378. Y Y

In order to compensate small errors due to non-'opposed antennasensitivity zeros, the sense antenna C is connected to the receiver 1through an ampliiier 9 which can be modulated. The amplitude reversibleadjusters 85 and 81 are arranged to apply a portion of each of thequadrature 20 cycle waves to the mixer 89, the output of which modulatesthe amplifier 9. l 'Thus by adjustment of the devices 85 and 81theOutput of the antenna C may be modulated to the proper depth and in theproper phase to correct the above errors.

In response to a Wave arriving at the antenna system, the receiver 1produces a 20 cycle Wave, related in phase with respect to a fixed phasereference such as the phase of the 20 cyclerroutput of the lter 69, byan angle equal to the azimuth of arrival of the Wave with respect to adirection of reference such as the line between the antennas N and S.The output of the receiver Y1 is applied to the filter 39 to remove any`Signal modulation other than the 20 cycle patresponding to the azimuth.A typical indication |05 is shown on the record illustrated in Fig. 2.

In a similar manner, the outputs of the other remote direction findersare filtered at 43 and 53. The output of the filter 43 is applied to thephase Shifters 45 and 41, which are arranged to provide small equal andopposite phase shifts. The impulse generators 49 and 5I are controlledby the shifted Waves to provide pulses before and after the peak of the20 cycle wave on the line 35. The resulting facsimile record lcomprisesa double line, as illustrated by the indication IOI shown in Fig. 2. Thecenter of the space between the two lines corresponds to the bearing.

The indication |03 is derived from the third direction finder in asimilar manner by means of the phase Shifters 51 and 59 and the impulsegenerators 55, 6I and 63. In this case the central line corresponds tothe peak of the 20 cycle Wave, and is derived from the impulse generator55 which is controlled directly by the output of thelter 53. v

To'avoid errorsr due to paper shrinkage and slip, as well as to save onpaper cost, both the bearing and time scales may be recorded as'thepaper passes through the machine. Scale marking voltages are derivedfrom the source 23 by the commutator devices I5 and l1, which may bearranged to break up the direct voltage of the source 23 to provideimpulse trains as shown in the following tables:

High speed commutator 15 Repetition Pulse durafrequcncy, tion, millisec-Purpose cycles/sec. onds 0.1 Mark 90 lines. 240 0.1 Mark 30 lines-omitsevery third Y pulse. 720 0.1 Mark 10 lines-omlts every third pu e. 300Square wave.. Biialf minute timing lines into as es. y

900 .do Break 1 minute timing lines into dots.

Low speed commutator 17 Repetition Pulse duraperiod, mintion, milliscc-Purpose l utes onds l5 50 Mark quarter hour lines.

5 50 Mark 5 minute lines-omits every third pulse. A

1 50 Mark 1 minute lines-omlts every fth pulse.

l Square wave Break 80 lines into dashes.

/ do Break 10 lines into dots.

All of the above impulse trains are combined in the mixer 61 and appliedto therprinter circuit of therecorder II. The resulting markings are il;lustrated in Fig. 2, where the 1 minute timing lines and, the ten degreebearing lines are shown only in the rectangle betweenthe0435 and 0440time lines and the 210 to 270 bearing lines, although actually these`lines are to be recorded over the entire sheet.

To provide aperiodic checkontlre accuracy of the system, a plurality ofsmall local oscillators may be arranged at cardinal'and primaryintercardinal points around each receiver and` clock controlled totransmit at predetermined: times. The resulting indications on therecord are shown at |01 (Fig. 2).

The indications obtained from different types of signals are shown bythe record of Fig. 2. The indication |03 represents a steady bearing.The blurred, variable width indication |05 is the result of anindefinite or rapidly swinging bearing. The indication l! is typical ofa slowly swinging bearing.

Under some circumstances a permanent record of bearings may not berequired. Fig. 3 illustrates a system for indicating simultaneously onthe screen of a single cathode ray tube the bearings taken from aplurality of remote direction nders. The remote direction iinders |02,|04, and are similar to the direction nder of Fig. l. The controlsystems |08, |09 and are likewise similar to the control system shown inFig. l. The phase Shifters, impulse generators, and the mixer B5, areall identical with the corresponding components of the system of Fig. 1and are designated by similar reference numerals. The indicatorcomprises a cathode ray tube ||3, provided with the usual vertical andhorizontal denection means H5 land IIT, and a radial pair of deflectionelectrodes H9. The electrodes ||'3 'are connected to the output of themixer 65.

-An impulse generator |2| is connected through a switch |23 to the inputof the mixer 65. The generator |2| is connected also to an eight to onefrequency divider |25, which may be a counter circuit or amultivibrator. The output of the device |25 is connected to control asquare wave generator |21, which is connected through a filter |29 and a90 phase shifter |3| to the remote direction finder control circuits|08, |09 and and to a deection control circuit |33. The circuit |33includes amplitude controls arranged to enable adjustment of thedeflection and bias voltages applied to the deflection means H5 and toproduce circular scanning of the cathode ray beam of the tube |3.

The operation and adjustment of the system is similar to that of thesystem of Fig. l, excep+u for the derivation of the control voltages andthe deflection control. The impulse generator |2| is used as a source,rather than a lower frequency sine Wave generator, for the calibrationof the deiiection circuits. 'Ihe frequency divider |25, square wavegenerator |21, and lter |29 cooperate in Well known manner to provide asine wave subharmonically related in frequency to the output of theimpulse generator |2I. The sine wave output of the phase shifter |3| isused to provide rotation of the directive patterns of the directionfinders, as described in the aforementioned Luck Patent No. 2,208,378and also to rotate the beam of the cathode ray tube i3 in synchronismwith the pattern rotation. The single impulse from the direction iinder|02 produces a single peaked radial deflection IM on the screen, and thedirection finders |04 and |06 produce double and triple peakeddeflections |33 and |31 respectivelyt `Scale markings |35 may beproduced on the face of the tube H3 for comparison with a fixed scalefor calibration, by closing the switch |23,

Yconnecting the generatorf|2| -to the mixer k|55-and thence to' theradial deflectiony electrode H9. The lines |35-will-appear at spacedpoints around the-'circumference -of'the scanning trace; representingequal angular divisions'of the V36O" trace.

The number of divisions is equal to the ratio Kof the frequency divider|25, which willnormally be 8.

IV claim asmy invention:

l. A system for recording the time and origin of radio transmissionincluding a facsimile recorder, a motor arranged to drive said recorder,means for producing alternating current synchronous with the scanning ofsaid recorder, a plurality of antenna arrays at spaced points,meansassociated with each of said arrays for providing a rotatingdirective pattern in response to said alternating current, a receiverconnected to each of said arrays so as to provide an output related inphase to said alternating current in accordance with the direction ofwave arrival, means for producing impulses in response to the output ofeach of said receivers, of characteristics distinguishable from theimpulses produced in response to the output of each of the others ofsaid receivers; means operated by said driving motor for producing timeand azimuth reference impulses, and means for actuating said recorder inresponse to all of said impulses.

2. A direction finding system comprising a control station and aplurality of direction finder stations at dierent locations, a recorderand a source of reference phase alternating current at said controlstation, means for supplying said reference phase alternating current toeach of said direction iinder stations, means at each of said directionfinder stations for producing in response to an arriving wave analternating current related in phase to said reference phase current inaccordance with the azimuth of arrival of said wave, and means foractuating said recorder in response to the alternating current producedat each of said direction finder stations- 3. A direction iinding systemincluding a plurality of differently located direction finders eachcomprising means for producing in response to an arriving wave a trainof sine Waves related in timing to the azimuth of arrival of said Waveat said direction nder, means for supplying all of said sine wave trainsto a common control station, and means responsive to said wave trains toprovide distinctive azimuth indications at said control station, saidlast mentioned means including a plurality of groups of impulsegenerators, each group being connected to respond to the wave trainproduced by one of said direction finders, phase shifting meansconnected between certain of said impulse generators and thecorresponding direction finders, said phase shifting means beingadjusted so that the outputs of the different direction nnders producetrains of groups of dierent numbers of impulses.

4. A radio direction finding system comprising a plurality of directionfinders, each arranged to produce, in response to an arriving wave, asinusoidal voltage related in phase to the azimuth of arrival of saidwave-at said direction finder; an impulse generator connected to theoutput of one of said direction iinders to produce a train of singleimpulses in response thereto, two other impulse generators connected tothe output of another of said direction nders through differentlyadjusted phase Shifters to produce a train of double impulses inresponse thereto, and three other impulse generators connected to theoutput of a. third` of said direction nders, tWo of said `last mentioned,impulse generators being connected to said thirdrdirecton nder throughdifferently adjusted phase Shifters and the third of said impulsegenerators being connected directly to said third direction nder, toproduce e. train of triple impulses n response thereto.

DAVID G. C. LUCK.

REFERENCES CITED The following references are of record in the file ofthis patent:

U'NITD STATES PATENTS Number Name Date 1,115,530 Hammond Nov. 3; 19142,214,342 Neufeld Sept. 10, 1940

